1. Field of the Invention
This invention relates to an adjustable device and in particular to an adjustable device which can be temporarily and rigidly secured in a position.
2. Description of Related Art
It is known to provide rigid and releasable positioning devices, an example of one such device comprises a metal base member having a hollow formed therein and a metal hemisphere adapted to fit the hollow. One of the base member and the hemisphere are magnetised thus, when the hemisphere is located in the hollow within the base member, it is fixed in position. If the hemisphere is manually moved with respect to the base member, then the orientation and angle of the flat surface of the hemisphere changes with respect to the base member. Thus, if an article were placed on the flat surface of the hemisphere, the orientation and angle of this article is changed with respect to the base member as a result of this movement.
The accurate positioning of articles is required in a number of situations. One situation is where the article is to be measured to produce a mould or a direct copy of the article. In order for accurate data regarding the three-dimensional structure of the article to be obtained, the entire surface of the article must be available for measurement by, for example, a probe. Therefore, the article must be positioned so that the underside of any overhanging regions may be measured to ensure that there are no re-entrant points.
An article where re-entrant points can occur is a tooth. It is desirable to obtain information which details the exact shape and configuration of a tooth as this information can be used to produce a copy of the tooth which can replace a damaged tooth as obviously, if a crown or bridgework is made from a replica tooth it is likely to be a better fit and will also feel more comfortable to the person receiving the new dentalware.
Another situation where accurate positioning is required is when directing a light beam from a source to a reflector and subsequently a detector. An example is in a laser interferometer where the relative movement of two objects may be measured. It is important that the light beam is detected at all times during the measurement process thus the alignment of the reflector with respect to the light source and detector must be maintained.